From: ptkwt@...1.aracnet.com (Phil Tomson)
Date: 2002-10-01T16:39:23+09:00
Subject: OO Perl -> Ruby

I'm wrapping a C library for a Binary Decision Diagram package using swig.  
The creator of the C library also created an extension for Perl  using xs. 
I'd kind of like to use a similar interface as their OO Perl extension.

Now in Perl you can 'bless' a reference so that it becomse an object.  
Here's what they did in their 'new' function:

package Cudd;
sub new {
    my $class = shift;
    my $numVars = shift || 0;
    my $numVarsZ = shift || 0;
    my $numSlots = shift || &Cudd::UNIQUE_SLOTS;
    my $cacheSize = shift || &Cudd::CACHE_SLOTS;
    my $maxMemory = shift || 0;
    my $manager = 
      Cudd_Init($numVars,$numVarsZ,$numSlots,$cacheSize,$maxMemory);
    bless \$manager, $class;
    return \$manager;
}

Now, I'm translating this into Ruby like:

class CuddClass
  include Cudd
  def initialize(numVars=nil,numVarsZ=nil,numSlots=nil,cacheSlots=nil,
                 maxMemory=nil)
    @numVars = numVars || 0
    @numVarsZ= numVarsZ || 0
    @numSlots= numSlots || Cudd::CUDD_UNIQUE_SLOTS
    @cacheSlots= cacheSlots || Cudd::CUDD_CACHE_SLOTS
    @maxMemory= maxMemory || 0
    #Cudd.Cudd_Init is defined on the C side:
    @manager= 
      Cudd.Cudd_Init(@numVars,@numVarsZ,@numSlots,@cacheSlots,@maxMemory)
  end
end

Now, in Perl, the $manager that gets returned by the Cudd_Init function 
gets blessed and becomes the reference to the object - the $manager 
reference can respond to a certain set of method calls on it's own.  
Blesssing $manager into the Cudd package also adds some additional 
methods that are defined in the Cudd package.  In Ruby, calling:
CuddClass.new will call CuddClass' initialize and return a reference to an 
instance of CuddClass which is different from what's happening in Perl. So 
the question is, what's the best way to translate this into Ruby?  I'm 
thinking that I could use method_missing to redirect unknown (or at 
least of unknown to CuddClass, but known to @manager) method calls to the 
@manager reference.

Phil